This invention relates to diving snorkels such as used by divers or swimmers.
Conventional snorkels comprise a snorkel conduit provided with an upper opening lying above the water surface during actual use of the snorkel, a mouthpiece lying under the water surface during actual use of the snorkel, and a lower opening including a non-return valve adapted to be opened downwards and lying under the water surface during actual use of the snorkel.
The known snorkel, for example, from Japanese Utility Model Registration Gazette No. 2536368 usually has its upper opening defined by a first tubular portion and a second tubular portion extending in parallel to each other. These first and second tubular portions are laterally communicate with each other via a passage. Between the first tubular portion and the second tubular portion, the conduit is substantially in a curved condition so that undesirable inflow of water into the mouthpiece through the upper opening can be obstructed as reliably as possible.
A quantity of water having flowed into the snorkel through the upper opening lying above the water surface during actual use of the snorkel must be forced out by a swimmer's expiration. Consequently, a larger quantity of water inflow will correspondingly increase a swimmer's physical fatigue. To alleviate such physical fatigue, it is required for the snorkel of well known art to obstruct the inflow of water through the upper opening as effectively as possible. While the snorkel of well known art intends to achieve this by curving the conduit, its inflow obstructing ability is not satisfactory.
Commonly to the conventional snorkels inclusive of the above-mentioned snorkel of prior art, a quantity of water staying immediately below the mouthpiece often generates turbulence as a swimmer attempts to purge out a quantity of water remaining within the snorkel by vigorous expiration. Such phenomenon may prevent the quantity of water from rapidly moving toward the upper opening. The expiration for purge thus utilized in vain will further increase the swimmer's physical fatigue.